The present invention relates to apparatus for measuring and transmitting data commensurate with electrical, mechanical and/or environmental parameters in the immediate vicinity of a high voltage conductor, and more specifically to such apparatus which includes means for directly transmitting the data to a location an unlimited distance from the measuring location.
High power, AC, transmission line parameters have been typically measured by the use of step down isolation voltage transformers where one end of the primary high voltage winding was conductively coupled to the high voltage line. The existence of a direct conductive link between the high voltage passing through the power line and ground typically exposed the measuring equipment to high voltage stresses, especially when hit by lightning strikes. Exposure to such high voltage stresses necessitated bulky and therefore expensive construction of such voltage or current measuring equipment to assure reliable operation and operator safety over extended periods of time.
It is desirable to measure potential, current, phase angle, temperature and/or other powerline and environmental parameters at arbitrary positions along the power line for short periods or continually. These measured values can be used to derive Fourier frequency components, power, power factor and other information associated with the operation of a power system, and to locate and diagnose anomalies in the use and transmission of electric power. Various power line sensors for use in dynamic line rating of electrical power transmission lines have been disclosed in the prior art; for example, see U.S. Pat. Nos. 3,438,896, 3,633,191, 4,158,810 and 4,268,818. A line-mounted sensor module which comprises electronic components contained within a metallic enclosure surrounding the conductor, that measures, digitizes and transmits the actual instantaneous value of parameters such as voltage, current, phase angle, and temperature to a remote ground receiver using UHF/microwave radio communications is disclosed in the referenced related patent and prior applications. Such a configuration avoids requirements for bulky and costly insulation structures to isolate equipment at ground potential from the high voltage conductor. This was accomplished by the interposition of a radio link instead of the typical direct conductive connection to ground from the power line. However, this system requires the ground receiving station to be within, at most a few miles of the sensor modules and, at the 950 Mhz frequency, requires line-of-sight between transmitter and receiver. Besides the distance restrictions, the ground based equipment is subject to tampering and damage by various means. It also requires maintenance which may be difficult and expensive in remote locations.